The fastigial nucleus (FN) of the cerebellum is one of the extramedullary regions in the central nervous system which is involved in neural regulation of the cardiovascular system, under conditions of both rest and stress such as exercise. Our objective, as a team of investigators in the fields of anatomy and physiology, is to utilize FN projections to brainstem cardiovascular nuclei as an implement mechanism to describe autonomic regulation of blood pressure and cardiac performance in the dog. First, neuroanatomical techniques of horseradish peroxidase and autoradiography will be used to describe projections of the FN to the brainstem nuclei and descending brainstem projections to the sympathetic preganglionic neurons of the thoracic spinal cord. The brainstem nuclei we will investigate are the nucleus of the tract (NTS) lateral reticular nucleus (LRN), nucleus gigantocellularis (NGC), nucleus paragizanlocellularis lateralis (PGCL) and nucleus raphe magnus (NRM). Secondly, brainstem nuclei which project to the thoracic cord, also will be confirmed electrophysiologically by stimulating their terminal axons in the intermediolateral cell column while recording antidronically-activated extracellular potentials of single cells in the brainstem. Thirdly, the cardiovascular control of the FN-activated brainstem sites will be correlated with anatomical and electrophysiological data by recording heart rate, blood pressure, ECG, left ventricular pressure and contractility before and after lesioning of the brainstem nuclei in question. This study will utilize the input of the FN to brainstorm nuclei subserving cardiovascular funcion, however, the specific role of the fastigial nucleus is not in question.